Throat plate



May 20, 1969 G. 1'. SMITH 3,444,704

THROAT PLATE Original Filed June 18. 1965 INVENT OR 6w [Fir/225%,

M rah/m ATTORNEYS United States Patent THROAT PLATE Gus T. Smith, Paducah, Ky., assignor, by mesne assignments, to Marvel Specialty Company, Inc., Paducah, Ky., a corporation of Kentucky Continuation of application Ser. No. 464,933, June 18,

1965. This application Jan. 29, 1968, Ser. No. 702,761 Int. Cl. D04b /54, 27/10, /00 U.S. Cl. 66125 6 Claims ABSTRACT OF THE DISCLOSURE A throat plate for a circular knitting machine in which the side and base wall at one corner of the U-shaped channel in the top surface of the guide plate which receives the yarn in normal running position and thus bears substantially all of the wear of the yarn, are provided with shallow recesses and in such recesses is disposed a thin preformed inlay of wear-resistant ceramic material having a base leg and an upright leg of a configuration to fit in the recesses and to lie with their exposed surfaces extending generally continuously with the corresponding channel walls, the inlay being retained in position in such recesses to receive the wear of the year. Preferably, the insert inlay is provided with an adherent coating of a metal wettable by solder on the surfaces thereof facing the underlying recess surfaces and the insert is held in position by means of a soldered joint adhering between the metal coating and the metalic base member of the throat plate. In one embodiment, the recesses may be cut away from the wall surfaces of the throat with the ceramic inlay being configured to match substantially with the shape of such recesses. In another embodiment, the thickness of the base of the U-shaped channel in the throat plate is reduced an appropriate amount, the ceramic inlay is disposed of in the proper location, and the remainder of the channel base is built up to its normal thickness by means of a shim which is preferably held in place by spot-welding.

This application is a continuation of application Ser. No. 464,933, now abandoned.

This invention relates to the art of guides for running strands of yarn and is concerned more particularly with an improved throat plate for circular knitting machines.

The provision of durable guides for rapidly moving strands of filamentitious textile material is hampered by the tendency of the yarn in time to erode the surface it engages. Synthetic strands, such as nylon, of relatively fine denier are particularly prone to produce severe wear of the guide surface. The problem is all the more acute in the case of throat plates for circular knitting mechines where the yarn passes over the yarnengaging edge of the plate at a sharp, compound angle. Thus, it is by no means uncommon for the yarn to produce after several weeks of operation a hairline slit of one-eighth inch or greater depth in the corner of the channel of the plate at the yarn-engaging edge. This slit tends to abrade the running strand, resulting in loose filaments and other undesirable damage to the yarn which ultimately leads to breakdown during the operation of the machine, requiring replacement of the throat plate at considerable expense.

The seriousness of this problem has led a number of workers in the art to propose modifications in the normal construction of the throat plate in the hope of achieving a practical solution. One of the more successful of these proposals is described and claimed in my earlier Patent 3,095,718, issued July 2, 1963, according to which the entire front section of the throat plate is replaced by a correspondingly shaped piece of wear-resistant ceramic 3,444,704 Patented May 20, 1969 material attached to the remainder of the plate by means of a tongue and grooved connection maintained against Separation by locking pins. The arrangement of my prior patent has proved eminently satisfactory for use with ma chines feeding a single strand to the needles or at the main feed position of multi-feed machines. In a single feed circular knitting machine, yarn is fed to the needles from a single point on the circular locus defined :by the needle bed to produce a single course of knitted stitches upon each revolution of the cylinder carrying the needle bed. Only a single strand of yarn is fed to the needles at a time for active knitting, even though more than one strand may be employed during the over-all operation to produce a pattern or some other effect. In a multi-feed machine, at least one secondary or auxiliary feed position, in addition to the main feed position corresponding to that of a single feed machine, is provided at a spaced point on the circular locus so as to simultaneously feed a plurality of strands for active knitting on the needles during the revolution of the needle cyclinder. The desire for greater production on the part of the commercial knitter in recent years has made the use of multi-feed machines increasingly attractive.

In the knitting on multi-feed circular machines of articles where back-and-front knitting is involved, as in forming the heel and toe of hosiery, it is the yarn at the main feed position that remains in action during the periods of back-and-forth knitting, the yarns from the secondary feed position or positions being disengaged until operation in the normal direction is resumed. During these periods, the main feed yarn, of course, oscillates back-and-forth across the mouth of the channel of the throat plate as the needle cylinder changes direction. As the design of my earlier patent above identified furnishes wear-resistant ceramic material across the entirety of the yarn-engaging edge of the plate, it is ideally suited for service at the main feed position.

However, in at least certain commercial multi-feed machines, such as that known in the art as the Singer- Fidelity, the location of the secondary feed position coincides with a point on the needle path where the needles are in elevated position, allowing the latches of the needles to swing outwardly under the action of centrifugal force as the cylinder rotates at high speed. The disposition of the throat plate at the secondary position is such that the lower surface of the plate is engaged by the latches when swung out as just described. This rubbing contact between the needle latches and the throat plate undersurface is not especially objectionable so long as the undersurface of the plate is steel, giving steel-tosteel contact. However, if a throat plate modified in accordance with my prior patent is mounted at the secondary feed position, steel-to-cerarnic contact results, the consequence of which is severe wear in a relatively short period of the needle latches, requiring replacement by new needles.

In addition to the excessive wear on the needle latches as just described, the provision of wear-resistant ceramic material across the full expanse of the throat plate as is characteristic of my prior design is unnecessary for the needs of the secondary feed position plate. At the secondary position, the yarn does not oscillate across the face of the plate since it does not enter into back and forth knitting but remains essentially constantly at one corner of the plate, lifting from that corner when the feed fingers are taken out of action and returning thereto when the feed fingers are restored to operative position and tension is imposed on the yarn. Consequently, the wear on the throat plate at the secondary position is concentrated generally at one of its corners and, other than at this corner, the ceramic material serves no significant function and merely adds unnecessarily to the cost of the plate.

In a companion application, filed concurrently herewith, S.N. 465,018 now U.S. Patent No. 3,392,549, one form of improved throat plate especially adopted for use at the secondary feed point of circular knitting machines is disclosed and claimed. According to the invention of this application, there is produced in the corner of the plate corresponding to the running position of the yarn a recess extending into both walls defining the corner, preferably in the shape of a 270 sector of a circle, and an insert of wear-resistant material having a shape mating with that of the recess is placed therewithin with its exposed end face generally fiush with the end face of the plate. In order to avoid having the yarn snagged in the joints between the insert and the adjacent edges of the plate, the insert is turned slightly about its longitudinal axis so that the surface at the joints onto which the yarn moves is slightly depressed in relation to the surface from which the yarn departs.

While the design as just described was formed to give quite satisfactory results for most multi-feed circular knitting machines, some machines were discovered to be subject in practice to a most surprising aberration in that the yarn instead of seating squarely in the corner in its normal running position, tenderly to assume a location on the front edge of the plate some one-quarter inches or more from the corner. As the yarn during knitting extends from the plate to a point well in advance of the plate on the circular path of the cylinder and is under significant tension to regularize stitch formation, the assumption by the yarn of a position outside the leading corner of the plate was entirely unexpected and still cannot be explained. However, the fact remains that this phenomenon was encountered a sufficient number of instances as to necessitate efforts to further modify the design so as to accommodate this aberration along with normal running behavior.

It was quickly realized that the answer did not lie simply in increasing the diameter of the recess and mating insert. The permissible thickness of the plate is closely determined by the spatial limitations in the machine and as the diameter of the recess is increased, the point is soon reached where the remainder of the plate thickness is too thin for the structural needs of the plate. The possibility was then conceived of adapting the alternative embodiment of the above mentionedtapplication, in which the insert was of elbow shape, to the form of a thin inlay with its base arm extended sufficiently from the corner of the plate to accommodate any yarns running outside the corner. Although this arrangement lacked the snug engagement between the recess and insert inherent in the basic embodiment, the inlay could nonetheless be effectively held in place by means of a solder joint as broadly disclosed and claimed in another companion application filed concurrently herewith, S.N. 465,019.

Efforts to incorporate the non-snagging joint feature in the new insert inlay proved the extension of the base arm to be a complicating factor but it was then appreciated that this problem could be solved in more direct fashion by extending the length of the base arm of the insert inlay over more than one-half of the width of the throat plate channel. In this way, yarn descending as the carrier arms dropped into operative position maintained contact with the insert from the beginning without the necessity of passing from any part of the plate onto the inlay. On the other hand, the expense of constructing the entire front section of the plate of ceramic was still avoided.

The formation of an extremely shallow recess, as required by the new insert inlay, in the walls of the plate defining one front corner developed into a further problem. While the steel of the plates can be fashioned by grinding without undue difficulty, the removal of only a portion of the area of the corner walls, particularly to a depth of a few thousands of an inch, calls for considerable skill in the machinist. Moreover, squaring of all the sides of the recess in order that the insert inlay might seat snugly without gaps at the joints is next to impossible. To solve this problem, the idea was conceived of removing the entire surface of the base wall of the plate channel to the necessary depth, affixing the insert inlay in place, and then attaching a skim of complementary configuration and thickness to the base wall, as by means of spot welding, for example. In this manner, the critical thickness of the plate at the point of support for the yarn carrier arms is maintained. In the case of the other wall at the corner, restoration of the full thickness in the area in excess of that occupied by the insert inlay is unnecessary.

Two embodiments illustrating the application in practice of the discoveries recounted above to an actual throat plate are described in the following detailed description which should be read in conjunction with the accompanying drawings in which:

FIG. 1 is a top plan view looking down on one type of conventional throat plate equipped with an insert in accordance with the present invention;

FIG. 2 is a front elevation of the plate of FIG. 1;

FIG. 3 is an enlarged cross-section taken substantially along line 3-3 of FIG. 1;

FIG. 4 is a diagrammatic perspective view showing a plate as in FIG. 1 in operative association with a typical yarn feed finger and the needles of the knitting machine;

FIG. 5 is a greatly enlarged perspective of the insert inlay of the throat plate of FIG. 1; and

FIG. 6 is a view similar to FIG. 1 of a slightly different style of plate.

Turning now to a detailed description of the invention a illustrated in FIGS. 1-4, the numeral 10 is used to generally designate the throat plate which, except as hereinafter indicated, may be of any conventional design known in the art. Typically, such a plate, as is readily apparent from the drawings, takes the form of a fairly flat, generally rectangular block-like member, usually machined out of steel or the like. One side face 12 of this element (which serves as the front face when the plate is oriented in its conventional operative position) is shaped in whatever manner may be needed as to conform generally with the spatial considerations of the knitting machine at the point at which the plate is to be utilized. For example, one corner may be notched, as at 14. The upper portion of the untouched corner of side 12 may be, and ordinarily is, slightly beveled as indicated at 16. In the top face 18 of the element is a channel 20, of generally U-shaped cross-sectional configuration, extending from the front side 12 to the opposite or rear side 22. Channel 20 extends in depth well over one-half of the thickness of the block-like element and is defined by a bottom wall 24 and two opposite, upstanding side walls 26 and 28. In the flange-like portions flanking channel 20, there are provided holes 30, 30' for attaching the throat plate into operative position on the undersurfaces of the latch ring the knitting machine and these holes 30, 30' are preferably elongated in a direction parallel to channel 20 to facilitate precise radial adjustment of the front face of the plate. Dependent upon the type of circular knitting machine with which the plate is to be associated, a transversely elongated aperture may be for-med in bottom wall 22 of channel 18 somewhat nearer front side 12 than rear side 20, or bottom wall 22 may be left solid, as appears in the drawings.

Up to this point, the description has dealt with only those features conventional to throat plates known in the art. In accordance with the present invention, a recess 32 is provided in the front section of the base 24 and one side wall, e.g. side wall 26, of channel 20 so as to receive the insert inlay 34. As can be best seen from FIG. 5, insert inlay 34 is fashioned of a thin sheet of wear-resistant ceramic 36 of a type hereinafter defined in the shape of an elbow having an elongated base leg 38 and an upstanding short leg 40. The outside faces of insert inlay 34 are provided with a thin metallic coating 41, in a manner and for a purpose that will be described later. Base leg 38 is of a length stretching well in excess of one-half of the transverse dimension of channel 20 so as to extend when in assembled position over a major portion of that dimension. The shape of recess 32 is, of course, so selected as to correspond to the shape of insert inlay 34.

Preferably, recess 32 is formed in the plate by removing from the entire area of the base wall 22 a thickness of material corresponding to the overall thickness of inlay 34 and by removing a similar thickness from along the entire length of side wall 26 to a point slightly exceeding the height of short leg 40, to produce a shallow indentation, shown at 42. As the form of the plate is ordinarily obtained by machining a solid block, the removal of the extra thickness beyond that which is normally required poses no problem. An additional grinding step may be needed for the side wall indentation 42 but this can be carried out without difiiculty. On account of the confined space available for such a grinding step to be carried out, the formation of a rounded rather than a square edge at the top of the side wall recess, as at 44, may be inevitable. However, the path of the yarn during the operating cycle of the machine is such that presence of a rounded edge at this particular point can be readily tolerated, as will be explained subsequently.

When the plate is ready, the insert inlay 34 is secured in place at the corner by means of a soldering technique described more fully in my related application, 465,019, now abandoned. The bond formed by the solder is shown in exaggerated thickness at 45. Thereafter, the remainder of the area of the base wall 22 must be built up to the necessary original thickness in order that the operative portion of the yarn carrier fingers will be maintained precisely unchanged. This is accomplished by shaping a thin shim tool steel or the like to conform to the shape of the channel base, less the area of the inlay 34, and attaching this shim to the base wall 22, preferably by means of spot-welding, indicated at 46. By spacing the spot welds in close proximity as shown in the drawing, the structural strength of the joint between the shim and the remainder of the plate is essentially as high as an unmodified plate so that the plate constructed according to this invention is no less durable in practice than conventional plates.

If desired, a similar shim can be provided to fill out the remainder of the side wall recess 44. This measure, however, is not necessary to the utility of the modified plate as the side walls perform no function during the operation of the machine. Consequently, the balance of the recess 44 can be left open as appears in the drawings.

FIG. 6 illustrates the ease with which the plates of this invention can be altered to meet the peculiar requirements of a given knitting machine. In the alternative embodiment here seen, one side of the front of the front face 12' of the plate is cut away along an oblique angle, as at 14", instead of being merely notched as at 14 in the main embodiment. This alternative configuration can be produced merely by grinding away the desired portion of the plate assembly, using a diamond cutting wheel for removing at least those sections filled in by ceramic material. In other respects the plate of FIG. 6 is the same as that of FIGS. 14.

Where the path of the yarn leaving the throat plate is such that the yarn passes from the mouth of the channel in a direction having an appreciable downward component, it will be apparent that the front face 40 of the insert 34 cannot project beyond the plane of the front face 42 of the plate 10. Otherwise, a sharp edge would be presented that would damage the yarn. For this reason, the front face of the insert is at least flush with the front face of the plate and, preferably is very slightly recessed inwardly thereof.

The function of the insert as described in connection with FIGS. l-4 will become somewhat clearer from a consideration of FIG. 5. FIG. 5 is a diagrammatic perspective view of the throat plate modified as in FIGS. l-4 in operative position at the auxiliary feed point of the knitting machine, all parts of which with the exception of a fragment of a yarn carrier finger F, and a few of the knitting needles N, are omitted for sake of clarity. As has already been mentioned briefly, in contrast to the main feed position where the yarn is normally caused to oscillate back and forth at some period during the over-all knitting cycle, the yarn at the auxiliary feed point moves consistently in one direction during the time it is engaged in active knitting. Thus, with the needle cylinder rotating in a counter-clockwise direction indicated by the arrow adjacent the needles N, the yarn designated Y remains at the corner defined by the intersection of front side 12 and channel walls 22, 24, where the insert 34 is mounted. Obviously, if the needle cylinder normally rotates in the opposite or clockwise direction, the opposite corner of the channel would be selected for the provision of the insert.

A necessary incident to the operation of a multi-feed machine is periodic engagement in and disengagement from the knitting operation of the yarn being fed at the auxiliary feed point. As shown in FIG. 5, the yarn of feed finger F is in normal operative position with the yarn flowing through the feed opening therein angularly to the corner as just described and thence downwardly and angularly to the revolving array of knitting needles N. When the auxiliary yarn is to be disengaged from knitting, the feed finger F is moved by mechanical instrumentalities conventional to the knitting machine and forming no part of the present invention, to a position of considerable elevation with respect to the throat plate. The yarn, of course, shares in this movement to the extent permitted by the tension therein, sliding upwardly out of the corner along the front edge of insert surface 38 and thence along the front edge of channel surface 24 until displaced entirely away from the throat plate. The extent of the vertical displacement of the feed finger F is such that the rounded edge 44 of the side wall recess 42 offers no serious resistance to the passage of the yarn upward along the corner. Consequently, while measures to provide a smoother transition between the surfaces of leg 40 of the inlay and the adjacent surface of side wall 26 can be adopted if desired, they are not essential to the smooth operation of a machine using one of the present plates. Thereafter, when the auxiliary yarn is again to be introduced into knitting, the feed finger F drops back into operative position and upon reengagement of the auxiliary yarn with the knitting needles, the yarn is pulled across the front edge of channel wall 22 into the corner reinforced by insert 34. It will be seen that by virtue of the extension of the base leg 38 of the insert inlay over a major portion of the width of channel 20, the yarn drops directly into contact with the surface and/ or edge of the ceramic layer 36 of this leg without first contacting the surface of the plate elsewhere. As employed herein, the term major portion means a length well over one-half and preferably three-quarters of the width of the channel 20. When the particular cyclical path of movement of the yarn at the secondary feed point during the several phases of the knitting operation is kept in mind, significance of the critical relationship of the insert surfaces is more readily comprehended.

The ceramic material from which the insert of this material is constructed is very commonly known in the art at the present time. One satisfactory ceramic may consist of the type of ceramic material which is described in US. Patent No. 2,369,266 to Thurnauer, issued Feb. 13, 1945. It is not necessary, however, that the ceramic have the electrical properties therein described, although these may be desirable in some instances. Ceramics having prop- 7 erties satisfactory for the manufacture of inserts according to this invention may be identified by the following characteristics A wide line of suitable ceramic materials of varying chemical constituents as well as mechanical properties are sold by the American Lava Corporation under the trade name AlSiMag and a number of technical bulletins describing the variety of products that can be obtained from the company, of which special mention can be made of Bulletins Nos. 624 and 622. US. Patent No. 2,214,703 to Thurnauer also describes ceramic material satisfactory for the purposes of the present invention.

Once the ceramic insert inlay is fashioned into the desired configuration required for the particular style of plate with which it is to be assembled, it is prepared for soldering by having a thin layer of a metal capable of bonding with solder applied to its outside surfaces, i.e. those surfaces which seat against the plate proper. The details of the procedures used for applying this layer are fully described in my application, S.N. 465,019, now abandoned, already referred to, to which reference can be had.

The metal-coated insert inlay is now ready to be soldered in position in the corner of the plate. The preferred type of solder and other details are again given in the aboveidentified application and will not be repeated here. Although the use of a solder bond is considered the optimum mode of retaining the insert inlay in operative position, it will be obvious that other techniques could be substituted without departing from the broad spirit of the invention.

Where words of orientation such as front and rear, top, back, depressed, elevated and the like have appeared in the aforegoing specification, such usage is intended to be for purposes of description only and not by way of limitation since they are obviously relative to the orientation of the machine as a Whole or some other points of reference.

Having thus described the invention, that which is claimed is:

1. A throat plate for a circular knitting machine comprising a metallic base member having formed therein an elongated generally U-shaped channel open at at least one end, the yarn passing out of said channel end in a lateral and downward direction relative to the longitudinal axis of the channel, a thin preformed insert inlay of wear-resistant ceramic material disposed in a corner of said channel adjacent said open end and with one edge thereof substantially flush with said channel end, said insert inlay having a base leg extending across a substantial portion of the width of the channel and an upright leg extending at least partially up the height of the channel side wall, the dimension of said inlay in a direction parallel to the channel axis 'being such that the inlay receives the wear of the yarn, said channel base Wall and side wall being cut away to form a recess in which said inlay legs fit with the exposed surface thereof extending generally continuously with the corresponding channel walls, and means for holding said insert inlay in position in said recess.

2. The guide of claim 1 wherein the recess in said channel base wall for said inlay base leg is defined by shim shaped to conform to the shape of said base wall exclusive of said inlay and having the approximate thickness of said inlay, said shim being attached to said base wall.

3. The guide of claim 2 wherein said shim is attached by spot-welding.

4. The guide of claim 1 wherein said insert inlay is provided on the surfaces thereof contacting the base and side wall surfaces with an adherent coating of a metal wettable by solder and said means for holding the insert inlay in position is a solder joint between said contacting surfaces.

5. The guide of claim 4 wherein said solder is silver solder.

6. The improvement of claim 1, wherein said base leg extends across at least a major portion of said channel Width.

References Cited UNITED STATES PATENTS 2,686,958 8/1954 Eber et a1 29-473.1 2,896,434 7/1959 McKinnley et a1 66125 2,917,140 12/1959 Omlcy 29-4731 X 2,967,412 1/1961 Hoefer 66-125 3,004,733 10/1961 Spivey 66125 X 3,032,294 5/1962 Pieper 242157 3,062,028 11/1962 Mahler et al 66-125 3,065,533 11/1962 Dungan et a1 29473.1 X 3,100,339 8/1963 Bondley 29473.1 3,130,938 4/1964 Dysart 242-157 3,132,044 5/ 1964 Pearsall.

3,182,118 5/1965 De Proost et a1. 29473.1 X 3,284,174 11/1966 Zimmer 29-473.1 X 3,284,176 11/1966 Reed et al 29473.1 X

FOREIGN PATENTS 928,859 6/1963 Great Britain.

OTHER REFERENCES Pearsall et al.: Metal to Nonmetallic Brazing, Technical Rept. No. 104, Apr. 5, 1949, Research Laboratory of Electronics, Mass. Inst. of Technology.

Bender: High Temperature Metal Ceramic Seals, Ceramic Age, April 1954, pp. 15, 16, 17, 20, 21, 46-50.

MERVIN STEIN, Primary Examiner.

RONALD FELDBAUM, Assistant Examiner.

Disclaimer and Dedication 3,444,704.Gus T. Smith, Paducah, Ky. THROAT PLATE. Patent dated May 20, 1969. Disclaimer and dedication filed Jan. 25, 1977, by the assignee, M awel Specialty 00., Inc. Hereby enters this disclaimer and dedicates to the Public all claims of said patent.

[Oficial Gazette March 22, 1.977.] 

